From my first ascent at an indoor climbing gym (Carabiner’s in Fairfield, Connecticut), I was hooked, pun intended. Navigating a vertical faux rock face, reaching higher than seemed possible to grip fingertips and toes into the next color-coded holds was exhilarating…even before looking 40 feet down to where my belayer (an experienced guide/climbing partner), Mike Demchack stood, securing my rope from below. Even though said rope was “strong enough to support a car,” according to Demchack, the part of the brain that can’t differentiate real from simulated danger decided I was surely about to die. Adrenaline surged accordingly, and I rappelled down with a hardly warranted sense of accomplishment and survival.

One Toehold at a Time

Indoor climbing is a whole-body, cardiovascular workout, a year-round, individual sport (yet one usually done in tandem) in a social setting; it’s relatively inexpensive (on par with traditional gym memberships); demands focus and strategy, increases strength and flexibility, and is usually low-impact

Demchack, who has been climbing for five years, says he started because “I was a runner, but I had these little T. rex arms! Climbing is great for building upper-body strength.” Beyond the physical conditioning, Demchack says, are the mental benefits. “I go for a hard climb, and I fail and fail and eventually I get it, and it’s a great feeling, that perseverance and reward.”

Climbing gyms are popping up all over the country. Cort Gariepy, founder and CEO of Rockwerx a company that custom-builds climbing walls and facilities, and a veteran climber of natural and manmade facades, credits its surging popularity to women’s growing interest in the sport. The original indoor climbing spaces were housed in industrial buildings—anywhere with high ceilings and cheap rent. While there was an undeniable allure to the raw, gritty atmosphere—akin to an old-school boxing gym—this next generation of gyms appeal to a wider demographic, spanning gender, age, experience level and physical ability.

There are three basic climbing techniques offered at gyms:

• “Bouldering” is a freestyle climb along various short, color-coded routes on a faux-rock outcrop surrounded by thick safety mats. The only equipment needed is climbing shoes. The Flintstones aesthetic and popularity of bouldering with the 10-and-under set make it look deceptively simple, but it calls for—and quickly builds—serious physical strength and endurance.

• “Top roping,” involves a rope threaded through a bolt attached to the ceiling. One end of the rope is tied to the climber’s harness; the other is held by or clipped to a belayer on the ground, who takes up its slack as the climber ascends. The climber tries not to get distracted thinking of the unflattering and/or revealing belayer’s-eye view from below.

• “Lead climbing” most resembles the sport done outdoors, wherein a climber, tied to the rope, clips their end of the rope from one anchor (or quickdraw) to the next as they climb. Again, a belayer supports them from below, but if the climber slips they fall to their previous spot versus being immediately “caught” by a taut rope. The belayer may jump up to best counter their partner’s fall, resulting in a rather lovely duet, like aerialists in cargo pants.

Gearing Up

The walls are textured, so pants or knee-length shorts and long sleeves help prevent abrasions. Wear clothes that stretch, and layers (expect to sweat). Though other climbers and staff are focused on their own business, keep in mind that everyone’s looking up—so baggy shorts or thin cotton yoga pants might reveal more than your natural athletic abilities. All climbing gyms rent the equipment you’ll need—harness belt, shoes, chalk for sweaty palms and helmet if desired (usually required for children). After you get a climb or two under your belt, you’ll probably want your own Cheap Jordans shoes. Buy them snug—toes should be slightly curled—and opt for a thin rubber sole. Good vegan options include Five Ten, Evolv and Mad Rock. While magnesium carbonate chalk is nontoxic, it can cause respiratory irritation. A less-dusty alternative is the Metolius Eco Ball, which hangs from one’s harness, no chalk bag necessary.

High Ceilings, High Standards

When the chalk dust settled and my adrenaline buzz subsided, I got to wondering about the feat of heating, cooling and ventilating a space with 60-plus-foot ceilings. Gariepy says more people are opting for purpose-built spaces versus retrofitting old factories and warehouses, and that efficient HVAC is now more the norm than the exception. “I always ask when working with my clients, ‘How will you make your building perform better?’” Good air filtration systems are a must. “There’s a phenomenon called ‘white lung’ that people working in climbing gyms experience, where they cough up white stuff from the chalk dust,” he notes.

Many projects are being built to Leadership in Energy and Environmental Design (LEED) standards. Examples are Evolution Rock + Fitness (whose owner, Hilary Harris, is both a LEED architect and a former competitive climber), slated to open this year in Concord, New Hampshire, and Movement Climbing + Fitness in Boulder, Colorado, which generates 80% of its own power with rooftop solar panels, passive solar and solar thermal heaters.

Back at the gym, a three-year-old tightened her harness like a pro; two wiry men in their 60s took turns belaying for one another on a lead climbing wall. College guys gathered around a cargo net, some climbing it and others shaking it from below, all laughing. There were fliers for women’s nights and after-school camps. “One of the greatest traditions of the rock climbing community is controversy,” says Gariepy. “It’s just part of the sport—extremist, purist, all different cliques. The indoor gym provides that common ground for all of them.”